There is known a flexible fuel vehicle (FFV) loaded with a flexible-fuel engine capable of using fuel containing alcohol such as ethanol as a regeneratable resource in order to reduce petroleum consumption or the like.
As the alcohol-based fuel, there are known fuel (referred to as E100) containing 100% ethanol (more specifically, hydrous ethanol containing 5% water), and mixed fuel (referred to as E22) containing 22% ethanol and 78% gasoline. In some of the districts (such as countries), gasoline i.e. fuel (referred to as E0) which does not contain alcohol may be used in addition to the aforementioned alcohol-based fuels, as fuel for flexible fuel vehicles. Specifically, various fuels in which the alcohol content is arbitrarily set in the range of from 0 to 100% may be used in combination as vehicular fuels.
However, ethanol has a low vaporability and a low ignitability, and gasoline has a high ignitability. Thus, ignitability of fuel greatly differs depending on a difference in alcohol content. Consequently, various inconveniences may occur when these fuels are used in combination.
For instance, Patent Literature 1 discloses an inconvenience that occurrence of knocking is different depending on fuel to be used. In order to solve the aforementioned inconvenience, Patent Literature 1 discloses a configuration, in which the type of fuel in a fuel tank is detected by a fuel sensor, and an intake valve closing timing is changed according to the detection result.
Further, there is known an inconvenience that it is difficult to secure startability accompanied by a difference in ignitability as described above. Conventionally, in order to solve the aforementioned inconvenience, an auxiliary fuel tank for securing startability is provided independently of a normal fuel tank, and fuel having a low ethanol content and a high ignitability is introduced to the auxiliary fuel tank. At an engine start time, the engine is started by using the fuel in the auxiliary fuel tank, and during a normal operation thereafter, the fuel in the normal fuel tank is used.